1. Field of the Invention
The present invention relates to a novel, chemically amplified resist composition suited for use in micro-lithography.
2. Description of the Related Art
The miniaturization of a pattern rule has been demanded in order to cope with a recent tendency of LSI technology to higher integration and higher speed. Under such a circumstance, far ultraviolet lithography has been regarded promising as the next-generation of micro-lithography. Even a pattern of 0.3 xcexcm or less can be formed by far ultraviolet lithography, and use of a resist material exhibiting low light absorption makes it possible to form a pattern with side-wall angles nearly vertical to a substrate. In recent years, a technique making use of a high intensity KrF excimer laser as a far-UV light source has drawn attentions. There is accordingly a demand for the development of a low light absorbing and highly sensitive resist material which permits the use of the above-described technique for mass production.
From such a viewpoint, the recently-developed, chemically amplified positive type resist materials as described in Japanese Patent Publication (JP-B) No. 2-27660/""90 and Japanese Patent Provisional Publication (JP-A) No. 63-27829/""88 using an acid catalyst are particularly promising resist materials suited for far-UV lithography, because of their excellent characteristics such as high sensitivity, resolution and dry etching resistance.
Prior-art chemically amplified resists are however accompanied with the problems such as PED (Post Exposure Delay) that line patterns have a T-top profile, in other words, patterns become thick at the top, when the dwelling time from exposure to PEB (post exposure bake) is extended; and a so-called xe2x80x9ctrailing phenomenonxe2x80x9d that patterns in the vicinity of a basic substrate, particularly, a substrate made of silicon nitride or titanium nitride are widened.
It is presumed that the T-top profile results from lowering in the solubility of the surface of a resist film, while the trailing phenomenon on a substrate results from lowering in solubility in the vicinity of the substrate.
In addition, during the time from exposure to PEB, a dark reaction for eliminating an acid-labile group proceeds, leading to a problem that the leaving size of the line of a positive resist decreases.
These problems are serious hindrance to practical use of the chemically amplified resist. Such problems of the conventional chemically amplified positive resist material not only make difficult dimensional control upon lithography but also impair dimensional control upon processing of a substrate by using dry etching [refer to: W. Hinsberg, et al., J. Photopolym. Sci. Technol., 6(4), 535-546(1993) and T. Kumada, et al., J. Photopolym. Sci. Technol., 6(4), 571-574(1993)].
It is understood that in these chemically amplified positive type resist materials, a basic compound in the air or on the surface of a substrate largely takes part in the problem of PED or trailing phenomenon on the substrate. An acid on the surface of a resist film generated by exposure to light reacts with a basic compound in the air and is thereby deactivated. The longer the dwelling time from exposure to PEB becomes, the more the amount of a deactivated acid increases, making it difficult to cause decomposition of an acid-labile group. An insolubilized layer is therefore formed on the surface and a pattern inevitably has a T-top configuration.
It is well known that addition of a basic compound is effective for overcoming PED, because it can suppress the influence of a basic compound in the air (as described in Japanese Patent Provisional Publication Nos. 5-232706/""93, 5-249683/""93, 5-158239/""93, 5-249662/""93, 5-257282/""93, 5-289322/""93, 5-289340/""93, 6-194834/""93, 6-242605/""94, 6-242606/""94, 6-263716/""94, 6-263717/""94, 6-266100/""94, 6-266111/""94, 7-128859/""95, 7-92678/""95, 7-92680/""95, 7-92681/""95, 7-120929/""95 and 7-134419/""95).
As the basic compound, a nitrogen-containing compound is well known and examples include amine compounds and amide compounds having a boiling point of 150xc2x0 C. or greater. Specific examples include pyridine, polyvinyl pyridine, aniline, N-methylaniline, N,N-dimethylaniline, o-toluidine, m-toluidine, p-toluidine, 2,4-lutidine, quinoline, isoquinoline, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, 2-pyrrolidone, N-methylpyrrolidone, imidazole, xcex1-picoline, xcex2-picoline, xcex3-picoline, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 2-quinolinecarboxylic acid, 2-amino-4-nitrophenol, and triazine compounds such as 2-(p-chlorophenyl)-4,6-trichloromethyl-s-triazine. Among them, pyrrolidone, N-methylpyrrolidone, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid and 1,2-phenylenediamine are typical examples.
Although the above-described nitrogen-containing compounds can ease the T-top problem at an acid dissociation constant pKa ranging from 2 to 6, they cannot control reaction, that is, acid diffusion upon use of a highly-reactive acid-labile group.
When a weak base is added, a dark reaction in PED proceeds at an unexposed portion, thereby causing a reduction in a line size (slimming) and a decrease in film thickness on the line surface. Addition of a strong base having a pKa of 7 or greater is effective for overcoming the above-described problem.
However, higher pKa does not always bring about good results. Even when a superstrong base such as DBU (1,8-diazabicyclo[5,4,0]-7-undecene) or DBN (1,5-diazabicyclo[4,3,0]-5-nonen), proton sponge or a quaternary amine such as tetramethylammonium hydroxide is added, a sufficient effect is not available.
The present inventors have carried out various investigations. As a result, it has been found that amines represented by formulas (I) to (III) and (1) to (4) having a carbonyl group, an ester group, or a carbonate group are highly effective for preventing a decrease in the thickness of a resist film and also for enlarging a focus margin and bringing about dimensional stability.
N(X)n(Y)3xe2x88x92n xe2x80x83xe2x80x83(I)
wherein, n stands for 1, 2 or 3, preferably 1 or 2, side chains Xs may be the same or different and each independently represents xe2x80x94R1xe2x80x94Oxe2x80x94R2 or xe2x80x94R1xe2x80x94C(xe2x95x90O)xe2x80x94Oxe2x80x94R61 (in which R1s are the same or different and each independently represents an alkylene group of 1 to 5 carbon atoms, R2s are the same or different and each independently represents a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms containing a carbonyl or ester group, and R61s are the same or different and each independently represents a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a carbonyl group, an ester group, an ether group, a hydroxyl group or a lactone ring, or R1 and R2, or R1 and R61 in the same side chain may be coupled together to form a ring); and side chains Ys are the same or different and each independently represents a hydrogen atom or a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain an ether or hydroxyl group. 
In the above-described formulas, R1s are the same or different and each independently represents an alkylene group of 1 to 5 carbon atoms, R2s are the same or different and each independently represents a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms containing a carbonyl or ester group, R3 represents a hydrogen atom or a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms, and R4s are the same or different and each independently represents a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a carbonyl, ester or ether group. 
wherein, R62 represents a linear or branched alkylene group of 1 to 5 carbon atoms, p stands for 0, 1 or 2 with the proviso that p+q=3, R63s are the same or different and each independently represents a hydrogen atom or a linear, branched or cyclic alkyl group of 1 to 15 carbon atoms which may contain an ether, carbonyl, ester or hydroxyl group, and R64s are the same or different and each independently represents a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a carbonyl group, an ester group, an ether group, a hydroxyl group or a lactone ring. 
wherein, R65s are the same or different and each independently represents a linear, branched or cyclic alkyl groups of 1 to 15 carbon atoms which may contain an ether, carbonyl, ester or hydroxyl group.
In another aspect of the present invention, there is also provided a positive type resist composition, which can comprise (A): one or more basic compounds selected from the group consisting of formulas (I) to (III) and formulas (1) to (4), (B): an organic solvent, and (C1): a base resin which is an alkali insoluble or sparingly soluble resin having an acidic functional group protected with an acid-labile group but becomes alkali soluble when the acid-labile group is eliminated, and (D): an acid generator; and optionally (E): a dissolution inhibitor.
In a further aspect of the present invention, there is also provided a negative type resist composition, which comprises (A): one or more basic compounds selected from the group consisting of formulas (I) to (III) and (1) to (4), (B): an organic solvent, and (C2): a base resin which is alkali soluble but becomes alkali sparingly soluble by crosslinking with a crosslinker, (D): an acid generator, and (F): a crosslinker which undergoes crosslinking by an acid.
The present invention relates to a resist composition containing one or more basic compounds selected from those represented by formulas (I) to (III) and (1) to (4).
Specific examples of the basic compounds represented by formulas (I) to (III) and (1) to (4) include, but not limited to, tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine, N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine, tris(2-methoxycarbonyloxyethyl)amine, tris(2-tert-butoxycarbonyloxyethyl)amine, tris[2-(2-oxopropoxy)ethyl]amine, tris[2-(methoxycarbonylmethyl)oxyethyl]amine, tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine, and tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine {corresponding to the formulas (1) and (III)}; tris(2-methoxycarbonylethyl)amine and tris(2-ethoxycarbonylethyl)amine {corresponding to the formula (I), (II) and (3)}; N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-[methoxycarbonyl)methoxycarbonyl]ethylamine, N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis (2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl )ethylamine, N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine, N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine, N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine, N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine, N-(2-hydroxyethyl)bis[2-(methoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)bis[2-(methoxycarbonyl)ethyl]amine, N-(2-hydroxyethyl)bis[2-(ethoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)bis[2-(ethoxycarbonyl)ethyl]amine, N-(3-hydroxy-1-propyl)bis[2-(methoxycarbonyl)ethyl]amine, N-(3-acetoxy-1-propyl)bis[2-(methoxycarbonyl)ethyl]amine, and N-(2-methoxyethyl)bis[2-(methoxycarbonyl)ethyl]amine {corresponding to the formula (I) and (II)}; N-butylbis[2-(methoxycarbonyl)ethyl]amine and N-butylbis[2-(2-methoxyethoxycarbonyl)ethyl]amine {corresponding to the formula (1) and (4)}; N-methylbis(2-acetoxyethyl)amine, N-ethylbis(2-acetoxyethyl)amine, N-methylbis(2-pivaloyloxyethyl)amine, N-ethylbis[2-(methoxycarbonyloxy)ethyl]amine, N-ethylbis[2-(tert-butoxycarbonyloxy)ethyl]amine {corresponding to the formula (I) and (2)}; tris(methoxycarbonylmethyl)amine and tris(ethoxycarbonylmethyl)amine {corresponding to the formula (I) and (3)}; N-butylbis(methoxycarbonylmethyl)amine and N-hexylbis(methoxycarbonylmethyl)amine {corresponding to the formula (I) and (4)}; and 62 -(diethylamino)-xcex4-valerolactone {corresponding to the formula (I)}.
As the organic solvent usable as Component (B) in the present invention, any organic solvent permitting dissolution therein of an acid generator, base resin, dissolution inhibitor or the like may be used. Examples of such an organic solvent include ketones such as cyclohexanone and methyl-2-n-amylketone, alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol and 1-ethoxy-2-propanol, ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether and diethylene glycol dimethyl ether and esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate and propylene glycol mono-tert-butyl ether acetate. They may be used either singly or in admixture of two or more, but an organic solvent usable in the present invention is not limited to them.
In the present invention, diethylene glycol dimethyl ether, 1-ethoxy-2-propanol or ethyl lactate in which the acid generator contained in the resist composition is most soluble, or propylene glycol monomethyl ether acetate which is a safe solvent, or a solvent mixture therewith is preferably employed among the above-described organic solvents.
Regarding a base polymer (C) of the present invention, a base resin (C1) which has an acidic functional group protected with an acid-labile group and is insoluble or sparingly soluble in alkali, but becomes soluble in an alkali by the elimination of the acid-labile group is usable for a positive type resist composition, while a base resin (C2) which is soluble in alkali but becomes sparingly soluble in alkali by crosslinking with a crosslinker is usable for a negative type resist composition. The xe2x80x9cinsoluble or sparingly soluble in alkalixe2x80x9d means that solubility in an aqueous solution of 2.38% by weight of TMAH (tetramethylammonium hydroxide) is 0 or less than 20 xc3x85/sec, and xe2x80x9csoluble in alkalixe2x80x9d means that solubility in an aqueous solution of 2.38% by weight of TMAH is 20 to 300 xc3x85/sec.
Examples of the base polymer used as the component (C) in the present invention for a KrF excimer laser resist of 248 nm in wavelength, EUV resist of 3 to 20 nm in wavelength, EB resist or X-ray resist include polyhydroxystyrene (PHS) and copolymers thereof with styrene, (meth)acrylate or maleimide-N-carboxylate; those of the base polymer for an ArF excimer laser of 193 nm in wavelength include (meth)acrylate polymers, alternating copolymers of norbornene and maleic anhydride, polynorbornene polymers and metathesis ring-opening polymerization type polymers; and those for an F2 excimer laser of 157 nm wavelength include the above-exemplified polymers substituted with fluorine. The base polymer (C) is however not limited thereto. In the above, xe2x80x9c(meth)acrylatexe2x80x9d means methacrylate or acrylate.
The base polymer (C1) usable for the positive type resist composition is obtained by substituting the hydrogen atom of the hydroxyl group of the phenol or carboxyl group of the base polymer (C2) with an acid-labile group. It is the common practice to lower the dissolution rate of an unexposed portion by such substitution.
As the acid-labile group, groups represented by the below-described formula (5) or (6), tertiary alkyl groups of 4 to 40 carbon atoms reprented by the below-described formula (7), trialkylsilyl groups of 1 to 6 carbon atoms and oxoalkyl groups of 4 to 20 carbon atoms are preferred among various groups. 
wherein, R6 and R9 each independently represents a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hetero atom such as oxygen, sulfur, nitrogen or fluorine, R7 and R8 each independently represents a hydrogen atom or a linear, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hetero atom such as oxygen, sulfur, nitrogen or fluorine, and a stands for an integer of 0 to 10, or R7 and R8, R7 and R9, and R8 and R9 may each be coupled together to form a ring.
Additional examples of R6, R9 or R12 include non-substituted or substituted aryl groups such as phenyl group and alkoxy-substituted phenyl groups, e.g., p-methylphenyl, p-ethylphenyl and p-methoxyphenyl and aralkyl groups such as benzyl and phenethyl.
Specific examples of the acid-labile group represented by the formula (5) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl, tert-amyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyranyloxycarbonylmethyl and 2-tetrahydrofuranyloxycarbonylmethyl groups.
Specific examples of the acid-labile group represented by the formula (6) include linear or branched acetal groups such as 1-methoxyethyl, 1-ethoxyethyl, 1-n-propoxyethyl, 1-isopropoxyethyl, 1-n-butoxyethyl, 1-isobutoxyethyl, 1-sec-butoxyethyl, 1-tert-butoxyethyl, 1-tert-amyloxyethyl, 1-ethoxy-n-propyl, 1-cyclohexyloxyethyl, methoxypropyl, ethoxypropyl, 1-methoxy-1-methylethyl and 1-ethoxy-1-methylethyl; and cyclic acetal groups such as tetrahydrofuranyl and tetrahydropyranyl groups. Preferred are ethoxyethyl, butoxyethyl and ethoxypropyl groups.
At least 0.1% of the hydrogen atoms of the hydroxyl groups of the base polymer may undergo intramolecular or intermolecular crosslinking via an acid-labile group (crosslinking group) represented by the following formula (8a) or (8b). 
In the above formulas, R19 and R20 each represents a hydrogen atom or a linear, branched or cyclic alkyl group of 1 to 8 carbon atoms. R19 and R20 may be coupled together to form a ring and if so, R19 and R20 each represents a linear or branched C1-8 alkylene group.
R21 represents a linear, branched or cyclic alkylene group of 1 to 10 carbon atoms and b stands for 0 or an integer of 1 to 10.
A represents an aliphatic or alicyclic, saturated hydrocarbon group, aromatic hydrocarbon group or heterocyclic group having a valence of a and 1 to 50 carbon atoms. The above-described group may have a hetero atom interposed. therein, or a part of the hydrogen atoms bonded to the carbon atoms of the group may be substituted with a hydroxyl group, a carboxyl group, a carbonyl group or a fluorine atom. B represents xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94NHCOxe2x80x94Oxe2x80x94 or NHCONHxe2x80x94. a stands for an integer of 2 to 8, and axe2x80x2 represents an integer of 1 to 7. They satisfy the following equation of a=(axe2x80x2+1).
R10, R11 and R12 in the formula (7) each represents a monovalent hydrocarbon group such as linear, branched or cyclic C1-20 alkyl group and it may contain a hetero atom such as oxygen, sulfur, nitrogen or fluorine. R10 and R11, R10 and R12, or R11 and R12 may be coupled together to form a ring. Alternatively, these groups may contain an oxygen atom, their hydrogen atom bonded to the carbon atom may be substituted with a hydroxyl group, or their two hydrogen atoms may be substituted with an oxygen atom toform a carbonyl-group.
Examples of the tertiary alkyl group represented by the formula (7) include tert-butyl, triethylcarbinyl, 2-ethyl-2-norbornyl, 1-methylcyclohexyl, 1-ethylcyclopentyl, 2-(2-methyl)adamantyl, 2-(2-ethyl)adamantyl and tert-amyl groups.
Examples of the trialkylsilyl group of 1 to 6 carbon atoms used as the acid-labile group include trimethylsilyl, triethylsilyl and dimethyl-tert-butylsilyl groups.
Examples of the oxoalkyl group of 4 to 20 carbon atoms used as the acid-labile group include a 3-oxocyclohexyl group and groups represented by the following formulas: 
The base polymer as Component (C) preferably has a weight average molecular weight ranging from 5,000 to 100,000. The molecular weights less than 5,000 may make the film forming property and resolution property inferior, while the molecular weights exceeding 100,000, on the other hand, may make resolution property inferior.
Examples of the acid generator as Component (D) include onium salts of the below-described formula (9), diazomethane derivatives of the formula (10), glyoxime derivatives of the formula (11), xcex2-ketosulfone derivatives, disulfone derivatives, nitrobenzyl sulfonate derivatives, sulfonate derivatives and imido-ylsulfonate derivatives. 
In the above-described formulas, R30s may be the same or different and each independently represents a linear, branched or cyclic alkyl group of 1 to 12 carbon atoms, aryl group of 6 to 12 carbon atoms or aralkyl group of 7 to 12 carbon atoms, M+ represents iodonium or sulfonium, Kxe2x88x92 represents a non-nucleophilic counterion and b stands for 2 or 3.
R31 and R32 each represents a linear, branched or cyclic alkyl group of 1 to 12 carbon atoms or halogenated alkyl group, aryl or halogenated aryl group of 6 to 12 carbon atoms, or aralkyl group of 7 to 12 carbon atoms.
R33, R34 and R35 each represents a linear, branched or cyclic alkyl group or halogenated alkyl group of 1 to 12 carbon atoms, aryl or halogenated aryl group of 6 to 12 carbon atoms, or an aralkyl group of 7 to 12 carbon atoms. R34 and R35 may be coupled together to form a cyclic structure and if so, R34 and R35 each represents a linear or branched alkylene group of 1 to 6 carbon atoms.
Examples of the alkyl group of 1 to 12 carbon atoms represented by R30 in the formula (9) include methyl, ethyl, propyl, butyl, cyclohexyl, 2-oxocyclohexyl, norbornyl and adamantyl groups. Examples of the aryl group of 6 to 12 carbon atoms include phenyl, alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl and m-tert-butoxyphenyl and alkylphenyl groups such as 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, ethylphenyl-4-tert-butylphenyl, 4-butylphenyl and dimethylphenyl groups. Examples of the aralkyl groups of 7 to 12 carbon atoms include benzyl and phenetyl. Examples of the non-nucleophilic counterion as Kxe2x88x92 include halide ions such as chloride ion and bromide ion, fluoroalkyl sulfonates such as triflate, 2,2,2-trifluoroethane sulfonate and nonafluorobutane sulfonate, aryl sulfonates such as tosylate, benzene sulfonate, 4-fluorobenzene sulfonate and 2,3,4,5,6-pentafluorobenzene sulfonate and alkyl sulfonates such as mesylate and butane sulfonate.
Examples of the alkyl group of 1 to 12 carbon atoms as R31 or R32 in the formula (10) include methyl, ethyl, propyl, butyl, amyl, cyclopentyl, cyclohexyl, norbornyl and adamantyl groups; those of the halogenated alkyl group of 1 to 12 carbon atoms include trifluoromethyl, 2,2,2-trifluoroethyl, 2,2,2-trichloroethyl and nonafluorobutyl groups; those of the C6-12 aryl group include a phenyl group and alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl and m-tert-butoxyphenyl groups and alkylphenyl groups such as 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl, 4-butylphenyl and dimethylphenyl groups; those of the halogenated aryl groups of 6 to 12 carbon atoms include fluorobenzene, chlorobenzene and 2,3,4,5,6-pentafluorobenzene groups; and those of the aralkyl group of 7 to 12 carbon atoms include benzyl and phenetyl.
Examples of the alkyl group of 1 to 12 carbon atoms, halogenated alkyl group of 1 to 12 carbon atoms, aryl group of 6 to 12 carbon atoms, halogenated aryl group of 6 to 12 carbon atoms and aralkyl group of 7 to 12 carbon atoms represented by R33, R34 or R35 in the formula (11), include those described in R31 and R32. Examples of the alkylene group of 1 to 6 carbon atoms for R34 or R35 include methylene, ethylene, propylene, butylene and hexylene groups.
Specific examples of the onium salt in the formula (9) include diphenyliodonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate, diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)phenyliodonium p-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate, tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate, triphenylsulfonium p-toluenesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate, bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate, tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate, triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfonium butanesulfonate, trimethylsulfonium trifluoromethanesulfonate, trimethylsulfonium p-toluenesulfonate, cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate, cyclohexylmethyl (2-oxocyclohexyl)sulfonium p-toluenesulfonate, dimethylphenylsulfonium trifluoromethanesulfonate, dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfonium trifluoromethanesulfonate and dicyclohexylphenylsulfonium p-toluenesulfonate.
Examples of the diazomethane derivative in the formula (10) include bis(benzenesulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(xylenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane, bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)diazomethane, bis(isoamylsulfonyl)diazomethane, bis(sec-amylsulfonyl)diazomethane, bis(tert-amylsulfonyl)diazomethane, 1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane, 1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane and 1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane.
Examples of the glyoxime derivative in the formula (11) include bis-o-(p-toluenesulfonyl)-xcex1-dimethylglyoxime, bis-o-(p-toluenesulfonyl)-xcex1-diphenylglyoxime, bis-o-(p-toluenesulfonyl)-xcex1-dicyclohexylglyoxime, bis-o-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime, bis-o-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime, bis-o-(n-butanesulfonyl)-xcex1-dimethylglyoxime, bis-o-(n-butanesulfonyl)-xcex1-diphenylglyoxime, bis-o-(n-butanesulfonyl)-xcex1-dicyclohexylglyoxime, bis-o-(n-butanesulfonyl)-2,3-pentanedioneglyoxime, bis-o-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime, bis-o-(methanesulfonyl)-xcex1-dimethylglyoxime, bis-o-(trifluoromethanesulfonyl)-xcex1-dimethylglyoxime, bis-o-(1,1,1-trifluoroethanesulfonyl)-xcex1-dimethylglyoxime, bis-o-(tert-butanesulfonyl)-xcex1-dimethylglyxoxime, bis-o-(perfluorooctanesulfonyl)-xcex1-dimethylglyoxime, bis-o-(cyclohexanesulfonyl)-xcex1-dimethylglyoxime, bis-o-(benzenesulfonyl)-xcex1-dimethylglyoxime, bis-o-(p-fluorobenzenesulfonyl)-xcex1-dimethylglyoxime, bis-o-(p-tert-butylbenzenesulfonyl)-xcex1-dimethylglyoxime, bis-o-(xylenesulfonyl)-xcex1-dimethylglyoxime and bis-o-(camphorsulfonyl)-xcex1-dimethylglyoxime.
Examples of the xcex2-ketosulfone derivative include 2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and 2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane.
Further examples of the acid generator (D) include disulfone derivatives such as diphenyldisulfone and dicyclohexyldisulfone, nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzyl p-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate, sulfonate derivatives such as 1,2,3-tris(methanesulfonyloxy)benzene, 1,2,3-tris(trifluoromethanesulfonyloxy)benzene and 1,2,3-tris(p-toluenesulfonyloxy)benzene, imido-ylsulfonate derivatives such as phthalimido-yl-triflate, phthalimido-yl-tosylate, 5-norbronene-2,3-dicarboxyimido-yl-triflate, 5-norbornene-2,3-dicarboxyimido-yl-tosylate and 5-norbornene-2,3-dicarboxyimido-yl-n-butylsulfonate.
Preferred examples include onium salts such as triphenylsulfonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate, triphenylsulfonium p-toluenesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate, and tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate; diazomethane derivatives such as bis(benzenesulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane, and bis(tert-butylsulfonyl)diazomethane; glyoxime derivatives such as bis-o-(p-toluenesulfonyl)-xcex1-dimethylglyoxime and bis-o-(n-butanesulfonyl)-xcex1-dimethylglyoxime; and naphthoquinonediazidesulfonate derivatives.
The above-exemplified acid generators may be used either singly or in combination.
The onium salts are excellent in rectangularity improving effects, while the diazomethane derivatives and glyoxime derivatives are excellent in standing-wave reducing effects. Use of these two types of acid generators in combination makes it possible to conduct fine profile control.
The acid generator is preferably added in an amount of 0.2 to 50 parts by weight, particularly, 0.5 to 40 parts by weight based on 100 parts by weight of the base resin in total. When the amount is less than 0.2 part by weight, an acid generation amount upon exposure is small, which may lead to inferior sensitivity and resolution. Amounts exceeding 50 parts by weight, on the other hand, lower the transmittance of the resulting resist, which may lead to inferior resolution.
Examples of the dissolution inhibitor serving as the component (E) include compounds having a molecular weight of 3000 or less whose solubility in an alkali developing solution changes by acid action, particularly, compounds obtained by partially or wholly substituting a phenol or carboxylic acid derivative having a molecular weight as low as 2,500 or less with an acid-labile substituent.
Examples of the phenol or carboxylic acid derivative having a molecular weight of 2500 or less include bisphenol A, bisphenol H, bisphenol S, 4,4-bis(4xe2x80x2-hydroxyphenyl)valeric acid, tris(4-hydroxyphenyl)methane, 1,1,1-tris(4xe2x80x2-hydroxyphenyl)ethane, 1,1,2-tris(4xe2x80x2-hydroxyphenyl)ethane, phenolphthalein, and thymolphthalein, while those of the acid-labile substituent include those exemplified above as the acid-labile group of the base polymer.
Preferred examples of the dissolution inhibitor include bis(4-(2xe2x80x2-tetrahydropyranyloxy)phenyl)methane, bis(4-(2xe2x80x2-tetrahydrofuranyloxy)phenyl)methane, bis(4-tert-butoxyphenyl)methane, bis(4-tert-butoxycarbonyloxyphenyl)methane, bis(4-tert-butoxycarbonylmethyloxyphenyl)methane, bis(4-(1xe2x80x2-ethoxyethoxy)phenyl)methane, bis(4-(1xe2x80x2-ethoxypropyloxy)phenyl)methane, 2,2-bis(4xe2x80x2-(2xe2x80x3-tetrahydropyranyloxy))propane, 2,2-bis(4xe2x80x2-(2xe2x80x3-tetrahydrofuranyloxy)phenyl)propane, 2,2-bis(4xe2x80x2-tert-butoxyphenyl)propane, 2,2-bis(4xe2x80x2-tert-butoxycarbonyloxyphenyl)propane, 2,2-bis(4-tert-butoxycarbonylmethyloxypheny)propane, 2,2-bis(4xe2x80x2-(1xe2x80x3-ethoxyethoxy)phenyl)propane, 2,2-bis(4xe2x80x2-(1xe2x80x3-ethoxypropyloxy)phenyl)propane, tert-butyl 4,4-bis(4xe2x80x2-(2xe2x80x3-tetrahydropyranyloxy)phenyl)valerate, tert-butyl 4,4-bis(4xe2x80x2-(2xe2x80x3-tetrahydrofuranyloxy)phenyl)valerate, tert-butyl 4,4-bis(4xe2x80x2-tert-butoxyphenyl)valerate, tert-butyl 4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate, tert-butyl 4,4-bis(4xe2x80x2-tert-butoxycarbonylmethyloxyphenyl)valerate, tert-butyl 4,4-bis(4xe2x80x2-(1xe2x80x3-ethoxyethoxy)phenyl)valerate, tert-butyl 4,4-bis(4xe2x80x2-(1xe2x80x3-ethoxypropyloxy)phenyl)valerate, tris(4-(2xe2x80x2-tetrahydropyranyloxy)phenyl)methane, tris(4-(2xe2x80x2-tetrahydrofuranyloxy)phenyl)methane, tris(4-tert-butoxyphenyl)methane, tris(4-tert-butoxycarbonyloxyphenyl)methane, tris(4-tert-butoxycarbonyloxymethylphenyl)methane, tris(4-(1xe2x80x2-ethoxyethoxy)phenyl)methane, tris(4-(1xe2x80x2-ethoxypropyloxy)phenyl)methane, 1,1,2-tris(4xe2x80x2-(2xe2x80x3-tetrahydropyranyloxy)phenyl)ethane, 1,1,2-tris(4xe2x80x2-(2xe2x80x3-tetrahydrofuranyloxy)phenyl)ethane, 1,1,2-tris(4xe2x80x2-tert-butoxyphenyl)ethane, 1,1,2-tris(4xe2x80x2-tert-butoxycarbonyloxyphenyl)ethane, 1,1,2-tris(4xe2x80x2-tert-butoxycarbonylmethyloxyphenyl)ethane, 1,1,2-tris (4xe2x80x2-(1xe2x80x2-ethoxyethoxy)phenyl)ethane, and 1,1,2- tris(4xe2x80x2-(1xe2x80x2-ethoxypropyloxy)phenyl)ethane.
In the present invention, the dissolution inhibitor is added preferably in an amount of 20 parts by weight or less, more preferably 15 parts by weight or less relative to 100 parts by weight of the solid content in the resist material. Amounts greater than 20 parts by weight increase the monomer component, may thereby deteriorating the heat resistance of the resist material.
Examples of the crosslinker as Component (F) include compounds having, in the molecule thereof, at least two hydroxymethyl groups, alkoxymethyl groups, epoxy groups or vinyl ether groups. Among them, substituted glycoluril derivatives, urea derivatives and hexa(methoxymethyl)melamine are used preferably.
Specific examples include N,N,Nxe2x80x2,Nxe2x80x2-tetramethoxymethylurea, hexamethylmelamine, tetrahydroxymethyl-substituted glycolurils, tetraalkoxymethyl-substituted glycolurils such as tetramethoxymethyl glycoluril, bis-hydroxymethylphenols, and condensation products between phenol compounds and epichlorohydrin or the like such as bisphenol A.
Particularly preferred examples of the crosslinker include 1,3,5,7-tetraalkoxymethylglycolurils such as 1,3,5,7-tetramethoxymethylglycoluril, 1,3,5,7-tetrahydroxymethylglycoluril, 2,6-dihydroxymethyl p-cresol, 2,6-dihydroxymethylphenol, 2,2xe2x80x2,6,6xe2x80x2-tetrahydroxymethyl bisphenol A, 1,4-bis-[2-(2-hydroxypropyl)]-benzene, N,N,Nxe2x80x2,Nxe2x80x2-tetramethoxymethylurea and hexamethoxymethylmelamine.
A crosslinker which undergoes crosslinking by an acid is preferred.
The amount of the crosslinker is not limited, but it is added in an amount of 1 to 25 parts by weight, preferably 5 to 20 parts by weight based on the whole solid content of the resist composition. The above-described crosslinkers may be used either singly or in combination.
As a base, conventionally employed bases other than the above-described ones may be used either singly or in combination. Examples of the conventionally employed bases include aliphatic primary, secondary or tertiary amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having a carboxyl group, nitrogen-containing compounds having a sulfonyl group, nitrogen-containing compounds having a hydroxy group, nitrogen-containing compounds having a hydroxyphenyl group, alcoholic nitrogen-containing compounds, amide derivatives and imide derivatives.
Examples of the aliphatic primary amine include ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, cetylamine, methylenediamine, ethylenediamine, and tetraethylenepentamine, those of the aliphatic secondary amine include dimethylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine, N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine and N,N-dimethyltetraethylenepentamine; and those of the aliphatic tertiary amine include trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, triisobutylamine, tri-sec-butylamine, tripentylamine, tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tridodecylamine, tricetylamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylmethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylenediamine and N,N,Nxe2x80x2,Nxe2x80x2-tetramethyltetraethylenepentamine.
Examples of the mixed amine include dimethylethylamine, methylethylpropylamine, benzylamine, phenethylamine and benzyldimethylamine. Specific examples of the aromatic amine or heterocyclic amine include aniline derivatives (ex. aniline, N-methylaniline, N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, ethylaniline, propylaniline, trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, N,N-dimethyltoluidine, etc.), diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene, pyrrole derivatives (ex. pyrrole, 2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, N-methylpyrrole, etc.), oxazole derivatives (ex. oxazole, isoxazole, etc.), thiazole derivatives (ex. thiazole, isothiazole, etc.), imidazole derivatives (ex. imidazole, 4-methylimidazole, 4-methyl-2-phenylimidazole, etc.), pyrazole derivatives, furazane derivatives, pyrroline derivatives (ex. pyrroline, 2-methyl-1-pyrroline, etc.), pyrrolidine derivatives (ex. pyrrolidine, N-methylpyrrolidine, pyrrolidinone, N-methylpyrrolidone, etc.), imidazoline derivatives, imidazolidine derivatives, pyridine derivatives (ex. pyridine, methylpyridine, ethylpyridine, propylpyridine, butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine, triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridone, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine, 2-(1-ethylpropyl)pyridine, amonopyridine, dimethylaminopyridine, etc.), pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives, piperidine derivatives, piperazine derivatives, morpholine derivatives, indole derivatives, isoindole derivatives, 1H-indazole derivatives, indoline derivatives, quinoline derivatives (ex. quinoline, 3-quinolinecarbonitrile, etc.), isoquinoline derivatives, cinnoline derivatives, quinazoline derivatives, quinoxaline derivatives, phthalazine derivatives, purine derivatives, pteridine derivatives, carbazole derivatives, phenanthridine derivatives, acridine derivatives, phenazine derivatives, 1,10-phenanthroline derivatives, adenine derivatives, adenosine derivatives, guanine derivatives, guanosine derivatives, uracil derivatives and uridine derivatives.
Examples of the nitrogen-containing compound having a carboxyl group include aminobenzoic acid, indolecarboxylic acid, amino acid derivatives (ex. nicotinic acid, alanine, arginine, asparatic acid, glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine, methionine, phenylalanine, threonine, lysine, 3-aminopyrazine-2-carboxylic acid, methoxyalanine, etc.); those of the nitrogen containing compound having a sulfonyl group include 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate; and those of the nitrogen-containing compound having a hydroxy group, nitrogen-containing compound having a hydroxyphenyl group or alcoholic nitrogen-containing compound include 2-hydroxypyridine, aminocresol, 2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine, diethanolamine, triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine, 2,2xe2x80x2-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidineethanol, 1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridineethanol, N-(2-hydroxyethyl)phthalimide and N-(2-hydroxyethyl)isonicotinamide. Examples of the amide derivative include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, and benzamide, while those of the imide derivatives include phthalimide, succinimide and maleimide.
Furthermore, the basic compound represented by the below-described formula (B)-1 or (B)-2 can be incorporated. 
wherein, R41, R42, R43, R47 and R48 each independently represents a linear, branched or cyclic C1-20 alkylene group, R44, R45, R46, R49 and R50 each independently represents a hydrogen atom, a C1-20 alkyl group or an amino group, or R44 and R45, R45 and R46, R44 and R46, R44 with R45 and R461, and R49 and R50 may each be coupled together to form a ring, and S, T and U each independently stands for an integer of 0 to 20 with the proviso that when S, T, U=0, each of R44, R45, R46, R49 and R50 does not contain a hydrogen atom.
The alkylene group for R41, R42, R43 R47 or R48 contains 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms. Specific examples include methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, n-pentylene, isopentylene, hexylene, nonylene, decylene, cyclopentylene and cyclohexylene groups.
The alkyl group for R44, R45, R46, R49 or R50, contains 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms. Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, hexyl, nonyl, decyl, dodecyl, tridecyl, cyclopentyl and cyclohexyl groups.
When R44 and R45, R45 and R46, R44 and R46, R44 and R45 and R46, or R49 and R50 form a ring, the ring has 1 to 20, preferably 1 to 8, more preferably 1 to 6 carbon atoms. In this ring, a C1-6, particularly C1-4 alkyl group may be branched.
S, T and U each stands for an integer of 0 to 20, preferably 1 to 10, more preferably 1 to 8.
Specific examples of the Compound (B)-1 or (B)-2 include tris{2-(methoxymethoxy)ethyl}amine, tris{2-(methoxyethoxy)ethyl}amine, tris[2-{(2-methoxyethoxy)methoxy}ethyl]amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine, tris[2-{(2-hydroxyethoxy)ethoxy}ethyl]amine, 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, 4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane, 1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, and 1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6.
In the present invention, the basic compound is preferably incorporated in an amount of 0.001 to 2 parts by weight, particularly 0.01 to 1 part by weight relative to 100 parts by weight of the whole basic resin. Amounts less than 0.001 part by weight may not bring about any incorporating effects, while those exceeding 2 parts by weight may excessively lower the sensitivity.
For efficient synthesis of the base of the present invention, Michael addition (exemplified by the formula IV) or alkylation (exemplified by the formula V) of an amine, and acylation or etherification (exemplified by the formula VI) of an alkanolamine are used either singly or in combination. The synthesis process is however not limited thereto. 
wherein, R and Rxe2x80x2 may be the same or different and each independently represents a substituted or unsubstituted methyl group, Rxe2x80x3 represents an alkylene group, Rxe2x80x2xe2x80x3 represents a substituted or unsubstituted methyl group (in the case of etherification) or a substituted or unsubstituted acyl group (in the case of acylation), and Z represents a leaving group such as halogen.